Abstract

Metastable electron traps and two-level systems (TLSs) are common in solid-state devices and lead to background charge movement and charge noise in single-electron and single-Cooper-pair transistors. We present measurements of the real-time capture and escape of individual electrons in metastable trapped states at very low temperatures, leading to charge offsets close to . The charge movement exhibits thermal excitation to a hysteretic tunneling transition. The temperature dependence and hysteresis can be explained by the coupling of a TLS to a quasiparticle trap.

Received 02 September 2008Accepted 10 October 2008Published online 31 October 2008

Acknowledgments:

We thank Denis Vion and Mark Dykman for discussions and F. Greenough, A. K. Betts, and others for technical support. P.J.M. gratefully acknowledges the hospitality and stimulation provided by Group Quantronique, CEA Saclay. The work was supported by the EPSRC-GB and by Royal Holloway, University of London.